Light sensor test unit, method of testing light sensor using the same and display apparatus

ABSTRACT

In a light sensor test unit, a test circuit is built in a display panel and connected to an output node of a light sensor which senses an intensity of an external light. When external light having a predetermined intensity is provided to the light sensor, the test circuit outputs a driving signal in response to a sensing signal output from the output node. A test pixel part includes pixels selected from a plurality of pixels arranged in the display panel and receives the driving signal from the test circuit to display a gray-scale corresponding to the driving signal. A brightness measurer measures a brightness corresponding to the gray-scale displayed in the test pixel part to compare the measured brightness with a predetermined brightness, thereby testing whether the light sensor built in the display panel is normally operated.

This application is a divisional of U.S. application Ser. No.12/260,420, filed on Oct. 29, 2008, which claims priority to KoreanPatent Application No. 2007-133496 filed on Dec. 18, 2007, and all thebenefits accruing therefrom under 35 U.S.C. §119, the contents of whichin its entirety are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light sensor test unit, a method oftesting a light sensor using the light sensor test unit, and a displayapparatus. More particularly, the present invention relates to a lightsensor test unit capable of testing a light sensor built in a displaypanel, a method of testing the light sensor, and a display apparatus.

2. Description of the Related Art

In general, a liquid crystal display (“LCD”) uses a liquid crystal whichis a passive light element incapable of emitting light itself, so thatan LCD panel receives a light from an exterior to display an image. TheLCD is classified into two types according to the light used to displaythe image. That is, the LCD is classified into a transmissive LCD whichuses an internal light generated from an inner light source to displaythe image and a reflective LCD which uses an external light generatedfrom an outer light source to display the image.

In a transmissive LCD, a backlight is arranged under the LCD panel toprovide a light to the LCD panel. The backlight consumes more than 70%of electric power used in the LCD. Thus, recently, a method whichreduces the power consumption of the backlight by decreasing anintensity of the internal light generated from the backlight issuggested when an intensity of the external light applied from theexterior to the LCD. In order to sense the intensity of the externallight, a light sensor is added to the LCD.

The light sensor is classified into two types. One is an internal typelight sensor formed through a thin film process on the display panel andbuilt in the display panel, and the other is an external type lightsensor attached to the exterior of one side of the display panel module.The external type light sensor is separable from the display panelmodule, so that it is easier to test whether the light sensor isnormally operated. However, the external type light sensor causes anincrease of the LCD in size and an assembling process of the LCD becomescomplicated by adding the external light sensor.

Accordingly, the built-in type light sensor has been widely employedrecently. However, when using the built-in light sensor, it is difficultto test the operation of the light sensor and a technique which teststhe built-in type light sensor has not been developed yet. Also, whenthe test process of the built-in type light sensor is omitted, areliability of the display panel decreases.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve theabove-stated problems, and an aspect of the present invention provides alight sensor test unit capable of effectively testing a light sensorwhich is built in a display panel, to sense an external light.

The present invention also provides a method of testing a light sensorusing the light sensor test unit.

The present invention also provides a display apparatus having the lightsensor test unit.

In an exemplary embodiment, the present invention provides a lightsensor test unit including a test circuit, a test pixel part, abrightness measurer, and a controller in order to test a light sensorwhich is built in a display panel.

According to an exemplary embodiment, the test circuit is connected toan output node of the light sensor and outputs a driving signal inresponse to a sensing signal output from the output node, when anexternal light having a predetermined intensity is applied to the lightsensor.

According to an exemplary embodiment, the test pixel part includespixels selected from a plurality of pixels arranged in the displaypanel, and receives the driving signal from the test circuit to displaya gray-scale corresponding to the driving signal. The brightnessmeasurer measures a brightness corresponding to the gray-scale displayedon the test pixel part, and the controller compares the measuredbrightness and the predetermined brightness to test whether the lightsensor is normally operated.

In another exemplary embodiment, the present invention provides a methodof testing a light sensor which is built in a display panel, to sense anexternal light using the light sensor test unit, the method includingproviding a predetermined external light to the light sensor, outputtinga sensing signal corresponding to the external light through an outputnode of the light sensor, outputting a driving signal to pixels selectedfrom a plurality of pixels arranged in the display panel in response tothe sensing signal, displaying a gray-scale corresponding to the drivingsignal through the selected pixels, measuring a brightness correspondingto the gray-scale in a region where the selected pixels are arranged,and comparing the measured brightness with a predetermined referencebrightness to test whether the light sensor is normally operated.

According to an exemplary embodiment, the outputting of the drivingsignal in response to the sensing signal further includes switching thesensing signal in response to an enable signal, outputting either afirst voltage or a second voltage as the driving voltage in response tothe sensing signal, and switching the driving signal in response to theenable signal.

According to an exemplary embodiment, the first voltage is a drivingvoltage of the display panel, and the second voltage is a groundvoltage.

According to an exemplary embodiment, the first voltage is output as thedriving signal when the sensing signal is at low level, and the secondvoltage is output as the driving signal when the sensing signal is athigh level.

According to an exemplary embodiment, prior to providing thepredetermined external light to the light sensor, further includesapplying a sensing gate signal in a high state to the light sensor tooutput the sensing signal in a high state through the output node,changing the sensing signal in the high state to the second voltage inresponse to the enable signal, and initializing the driving signalapplied to the selected pixels to the second voltage in response to theenable signal.

According to an exemplary embodiment, prior to outputting the drivingsignal to the selected pixels, further includes applying a gate signalto the pixels arranged in the display panel.

In another exemplary embodiment, the present invention provides adisplay apparatus which includes a backlight, a display panel, abacklight driver, and a display panel driver.

According to an exemplary embodiment, the backlight unit generates aninternal light. The display panel includes a plurality of pixelsarranged in a display area and receives the internal light to display animage, and a light sensor arranged in a black matrix area adjacent tothe display area and outputs a sensing signal corresponding to anintensity of an external light. The backlight driver receives thesensing signal to control an intensity of the internal light generatedfrom the backlight unit, and the display panel driver drives the pixelsarranged in the display panel.

According to an exemplary embodiment, the display panel includes a testcircuit which is connected to an output node of the light sensor andoutputs a driving signal in response to the sensing signal output fromthe output node of the light sensor when the external light having apredetermined intensity is provided to the light sensor in order to testthe light sensor. Thus, when the selected pixels receive the drivingsignal to display the gray-scale corresponding to the driving signalduring a test process of the light sensor, the light sensor test unituses the brightness measurer to measure the brightness corresponding tothe gray-scale, and tests whether the light sensor is normally operatedbased on the measured brightness.

According to the above, the test circuit connected to the light sensoris arranged on the display panel to test the light sensor which sensesthe intensity of the external light. The brightness of the pixelsoperated by the test circuit is measured by the brightness measurer.Thus, the light sensor test unit may test whether the light sensor isnormally operated or not.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects, features, and advantages of the presentinvention will become readily more apparent by reference to thefollowing detailed description when considered taken in conjunction withthe accompanying drawings in which:

FIG. 1 is a perspective view showing an exemplary embodiment of a lightsensor test unit according to the present invention;

FIG. 2 is a circuit diagram showing a connection relation between alight sensor, a test circuit, and a test pixel part of FIG. 1;

FIG. 3 is a waveform diagram showing signals of FIG. 2;

FIG. 4 is a circuit diagram showing an exemplary embodiment of a testcircuit according to the present invention;

FIG. 5 is a perspective view showing an exemplary embodiment of adisplay apparatus according to the present invention;

FIG. 6 is a plan view showing a display panel of FIG. 5; and

FIG. 7 is a circuit diagram showing a light sensor, a test circuit, atest pixel part, and a driving chip of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, the size and relative sizes of layers and regions may beexaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms, “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes”and/or “including”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 1 is a perspective view showing an exemplary embodiment of a lightsensor test unit according to the present invention.

Referring to FIG. 1, a light sensor test unit 100 is applied to test alight sensor 51 which is built in a display panel 50 which displays animage to sense an external optical environment (e.g., an intensity of anexternal light) of the display panel 50.

The built-in light sensor 51 is built in the display panel 50 through athin film process which forms a plurality of pixels in the display panel50, so that the light sensor 51 may not be tested through a testingmethod for an external type light sensor.

Thus, the light sensor test unit 100 includes a test circuit 110, a testpixel part 120, a brightness measurer 130, and a controller 140 in orderto test the built-in light sensor 51 in the display panel 50.

When an external light having a predetermined intensity is provided tothe built-in light sensor 51 in order to test the built-in light sensor51, the built-in light sensor 51 outputs a sensing signal correspondingto the intensity of the external light. The test circuit 110 isconnected to an output node of the built-in light sensor 51 to receivethe sensing signal and changes the sensing signal to a driving signal tooutput the driving signal. Circuit diagrams of the test circuit 110 willbe described in detail with reference to FIG. 2.

The test pixel part 120 includes pixels selected from the pixels formedin the display panel 50 and the selected pixels are electricallyconnected to the test circuit 110. Accordingly, the test pixel part 120receives the driving signal from the test circuit 110 and displays agray-scale corresponding to the driving signal. In the current exemplaryembodiment, the number of selected pixels of the test pixel part 120 mayvary.

The brightness measurer 130 is arranged adjacent to the test pixel part120 and measures a brightness corresponding the gray-scale displayed bythe test pixel part 120 when the test pixel part 120 displays thegray-scale corresponding to the driving signal. A brightness datameasured by the brightness measurer 130 is transmitted to the controller140, and the controller 140 compares a predetermined referencebrightness data with the measured brightness data to test whether thebuilt-in light sensor 51 is normally operated.

As shown in FIG. 1, the display panel 50 further includes a display areaDA on which an image is displayed, a black matrix area BA whichsurrounds the display area DA, and a peripheral area PA arranged outsideof the black matrix area BA. Since the pixels are arranged in thedisplay area DA and the test pixel part 120 includes the selected pixelsamong the pixels, the test pixel part 120 is positioned in the displayarea DA.

Meanwhile, a black matrix is arranged in the black matrix area BA inorder to block leakage of an internal light (e.g., an incident lightfrom a backlight (not shown) of the display panel) provided from a rearportion of the display panel 50. The built-in light sensor 51 isarranged in the black matrix area BA, and the black matrix is partiallyremoved in a region in which the built-in light sensor 51 is formed, sothat the external light may be applied to the built-in light sensor 51.

The test circuit 110 is arranged in the peripheral area PA, and the testcircuit 110 is electrically connected to the built-in light sensor 51and the test pixel part 120 through wires. Especially, the test circuit110 is arranged outside of a chip mounting area CA of the peripheralarea PA, in which a driving chip (not shown) is mounted on the displaypanel 50.

FIG. 2 is a circuit diagram showing a connection relation between thelight sensor, the test circuit, and the test pixel part of FIG. 1, andFIG. 3 is a waveform diagram showing signals of FIG. 2.

Referring to FIGS. 2 and 3, the built-in light sensor 51 includes asensing transistor Tss and a sensing capacitor Css. The sensingtransistor Tss includes a control electrode to which a first gate signalVg_sensor is applied, an input electrode to which a source signal Vg_ssis applied, and an output electrode outputting the sensing signal. Thesensing capacitor Css is connected between the output electrode and aterminal to which a direct bias voltage DC-bias is applied. In thecurrent exemplary embodiment, the output node N_out of the built-inlight sensor 51 is defined as a node to which the output electrode ofthe sensing transistor Tss and the sensing capacitor Css are connected.

During a test period P_ins, the first gate signal Vg_sensor having anegative voltage level (−) (for instance, from approximately −5V toapproximately −7V) is applied to the control electrode of the sensingtransistor Tss, and the source signal Vg_ss having a voltage level ofapproximately 0 volts is applied to the input electrode of the sensingtransistor Tss. When the predetermined external light Le is provided tothe sensing transistor Tss, the built-in light sensor 51 outputs a photocurrent corresponding to the external light Le. The photo current istransmitted from the output electrode to the input electrode of thesensing transistor Tss. Therefore, an electric potential of the outputnode N_out of the built-in light sensor 51 is dropped, and thus asensing signal in a low state is output from the output node N_out ofthe built-in light sensor 51.

According to an exemplary embodiment, the test circuit 110 includes afirst transistor T1, an inverter 111, and a second transistor T2. Thefirst transistor T1 includes an input electrode connected to the outputnode N_out, a control electrode receiving an enable signal Ven, and anoutput electrode connected to an input terminal of the inverter 111. Thesecond transistor T2 includes a control electrode receiving the enablesignal Ven, an input electrode connected to an output terminal of theinverter 111, and an output electrode connected to the test pixel part120. The inverter 111 includes a third transistor T3 and a fourthtransistor T4. The third transistor T3 includes a control electrode andan input electrode commonly connected to a first voltage terminal towhich a first voltage Vdd is applied and an output electrode connectedto the input electrode of the second transistor T2. The fourthtransistor T4 includes a control electrode connected to the outputelectrode of the first transistor T1, an input electrode connected to anoutput electrode of the third transistor T3, and an output electrodeconnected to a second voltage terminal to which a second voltage Vss isapplied.

During the test period P_ins, the first and second transistors T1 and T2are turned on in response to the enable signal Ven in a high state.According to an exemplary embodiment of the present invention, theenable signal Ven is a voltage signal having a voltage level ofapproximately 15V. The turned-on first transistor T1 provides thesensing signal output from the light sensor 51 to the inverter 111. Theinverter 111 outputs either the first voltage Vdd or the second voltageVss as the driving signal in response to the sensing signal inputthrough the first transistor T1. As shown in FIG. 3, during the testperiod P_ins, the first voltage Vdd has a voltage level of approximately4V to 5V, and the second voltage Vss includes a voltage level ofapproximately 0V.

Since the third transistor T3 is operated as a diode, the first voltageVdd is output from the output electrode of the third transistor T3. Whenthe sensing signal in a low state is output from the first transistorT1, the fourth transistor T4 is turned off, and as a result, the firstvoltage Vdd is output as the driving signal through the turned-on secondtransistor T2.

Meanwhile, each pixel arranged in the test pixel part 120 includes apixel transistor T_pixel and a liquid crystal capacitor Clc. The pixeltransistor T_pixel includes a control electrode receiving a second gatesignal Vgate, an input electrode connected to the output electrode ofthe second transistor T2, and an output electrode connected to theliquid crystal capacitor Clc. The liquid crystal capacitor Clc isarranged between the output electrode of the pixel transistor T_pixeland a common electrode to which a common voltage is applied.

During the test period P_ins, the second gate signal Vgate in a highstate is applied to the control electrode of the pixel transistorT_pixel. According to an exemplary embodiment of the present invention,the second gate signal Vgate includes a voltage level of approximately15V. When the pixel transistor T_pixel is turned on in response to thesecond gate signal Vgate, the first voltage Vdd output from the testcircuit 110 as the driving signal is charged to the liquid crystalcapacitor Clc through the pixel transistor T_pixel. Thus, the pixelsarranged in the test pixel part 120 display a gray-scale correspondingto the first voltage Vdd. Since a test procedure after theabove-mentioned procedure is described in detail with reference to FIG.1, the test procedure will be omitted.

According to an exemplary embodiment of the present invention, aprocedure which initializes the signal output from the test circuit 110may be performed prior to the above-mentioned test.

As shown in FIG. 3, the enable signal Ven is maintained at the highstate during an initialization period P_ini, the source signal Vg_ss ismaintained at a voltage level of approximately 4V to 5V, and the firstgate signal Vg_sensor has a voltage level that is increased toapproximately 15V.

Accordingly, during the initialization period P_ini, the electricpotential of the output node N_out of the built-in light sensor 51increases to approximately 4V to approximately 5V by the sensingtransistor Tss that is turned on in response to the first gate signalVg_sensor. The voltage output from the output node N_out is applied tothe control electrode of the fourth transistor T4 through the turned-onfirst transistor T1. Then, the fourth transistor T4 is turned on, andthe first voltage Vdd output from the third transistor T3 is dischargedthrough the fourth transistor T4. Thus, the test circuit 110 outputs thesecond voltage Vss as the driving signal during the initializationperiod P_ini. That is, the driving signal output from the test circuit110 may be initialized as the second voltage Vss.

As shown in FIG. 2, the display panel 50 further includes a readout bumpB_readout and a data bump B_data. The readout bump B_readout is used toelectrically connect a driving chip (not shown) that is mounted on thedisplay panel 50 and the built-in light sensor 51, and the readout bumpB_readout is electrically connected to the output node N_out of thebuilt-in light sensor 51 through wires. Also, the data bump B_data isused to electrically connect the driving chip and the pixels arranged inthe test pixel part 120 and to provide a data signal output from thedriving chip to the pixels. Accordingly, the data bump B_data iselectrically connected to the input electrode of the pixel transistorT_pixel arranged in the test pixel part 120.

Although not shown in FIG. 2, a plurality of gate lines and a pluralityof data lines are arranged in the display area DA of the display panel50. During a visual test procedure for test of the display panel 50, thedata lines are electrically connected with each other through aconnection line. Then, a test signal is applied to a test pad which isbranched from the connection line, so that the display panel 50 isoperated and the visual test is performed. The data lines may be dividedinto two groups that may be electrically connected to each other.

Meanwhile, a gate driver that outputs a gate signal to the gate linesmay be directly built in the display panel 50. During the visual testprocedure, control signal wires that receive various control signals fordriving the gate driver are electrically connected through a connectionline. Then, the test signal is applied to the test pad that is branchedfrom the connection line, thereby operating the display panel 50 andperforming the visual test.

When the visual test is completed, according to an exemplary embodiment,a laser trimming process is performed to electrically separate the linesfrom each other, which are electrically connected through the connectionline. During the laser trimming process, a first point LT1 and a secondpoint LT2 of the test circuit 110 may be laser trimmed. When the firstand second points LT1 and LT2 are laser trimmed, the output node N_outof the built-in light sensor 51 is electrically separated from the testcircuit 110, and the output terminal of the test circuit 110 iselectrically separated from the test pixel part 120. Since the testcircuit 110 is not necessary in the display panel 50 after testing thebuilt-in light sensor 51, the test circuit 110 is desirable to beelectrically separated from the built-in light sensor 51 and the testpixel part 120 through the laser trimming process.

However, when the laser trimming process is not applied, the first andsecond points LT1 and LT2 may not be laser trimmed. Therefore,hereinafter, according to another exemplary embodiment of the presentinvention, a test circuit employed in a display panel to which the lasertrimming process is not applied will be described.

FIG. 4 is a circuit diagram showing another exemplary embodiment of atest circuit according to the present invention. In FIG. 4, the samereference numerals denote the same elements in FIG. 2, and thus thedetailed descriptions of the same elements will be omitted.

Referring to FIG. 4, an enable terminal receiving an enable signal Venis electrically connected to a low voltage bump B_vgl arranged on adisplay panel 50. The low voltage bump B_vgl is arranged on the displaypanel 50 in order to receive a gate low voltage from a driving chip thatis mounted on the display panel 50 after a test procedure. The gate lowvoltage is provided to a gate driving circuit (not shown) which isdirectly formed on the display panel 50 through a thin film process anddecides an off level of a gate voltage output from the gate drivingcircuit.

Since the test procedure is performed before the driving chip is mountedon the display panel 50, only the enable signal Ven is applied tocontrol electrodes of a first transistor T1 and a second transistor T2through the enable terminal. When the test procedure is completed, theenable signal Ven is prevented from being applied, and the gate lowvoltage output from the driving chip during an active period of thedisplay panel 50 is applied to the control electrodes of the first andsecond transistors T1 and T2 through the low voltage bump B_vgl. Thus,the first and second transistors T1 and T1 are maintained in aturned-off state during the active period of the display panel 50, sothat the test circuit 120 and the test pixel part 120 are electricallyseparated from each other. Accordingly, the test pixel parts 120 maydisplay an image as well as pixels which display an image during theactive period of the display panel 50.

FIG. 5 is a perspective view showing another exemplary embodiment of adisplay apparatus according to the present invention, FIG. 6 is a planview showing a display panel of FIG. 5, and FIG. 7 is a circuit diagramshowing a light sensor, a test circuit, a test pixel part, and a drivingchip of FIG. 5.

Referring to FIGS. 5 and 6, a display apparatus 200 includes a backlight70 generating an internal light Li and a display panel 50 displaying animage using the internal light Li.

The backlight 70 is arranged under the display panel 50. Although notshown in FIGS. 5 through 7, the backlight 70 may include a light sourceor a plurality of light sources generating the internal light Li and alight guide unit guiding the internal light Li to the display panel 50.The light source may include one or more light emitting diodespositioned adjacent to a lateral surface of a light emitting unit.

The display panel 50 displays the image using the internal light Liprovided from the backlight 70. A built-in light sensor 51 that senses abrightness of an external light Le is arranged in a black matrix area BAof the display panel 50 in order to control an intensity of the internallight Li output from the backlight 70 according to the change ofexternal circumstance of the display apparatus 200.

As shown in FIG. 7, a driving chip 55 mounted on the display panel 50includes a circuit which receives a sensing signal output from thebuilt-in light sensor 51 to output a signal corresponding to theintensity of the external light Le. The circuit of the driving chip 55includes a first switch SW1, an op-amp 55 a, a second switch SW2, afeedback capacitor Cf, and an A/D converter 55 b.

The first switch SW1 is connected to a readout bump B_readout to receivethe sensing signal output from the light sensor 51 and selectivelyprovides the sensing signal to the op-amp 55 a. In the current exemplaryembodiment, the sensing signal is a voltage signal, for example.

The op-amp 55 a amplifies the sensing signal and provides the amplifiedsensing signal to the A/D converter 55 b. The amplified sensing signalis defined as an input voltage Vin of the A/D converter 55 b, and theA/D converter 55 b compares the input voltage Vin with a predeterminedreference voltage Vref to output a control signal in a digital form inorder to control a backlight driver 75.

In response to the control signal, the backlight driver 75 controls avoltage level of a driving voltage applied to the light source arrangedin the backlight 70. Accordingly, in an exemplary embodiment, thebacklight 70 outputs the internal light Li of which the intensity iscontrolled according to the level of the sensing signal output from thebuilt-in light sensor 51. That is, when the intensity of external lightLe is high, the backlight driver 75 decreases the intensity of internallight Li output from the backlight 70. Therefore, the display apparatus200 controls the intensity of the internal light Li of the backlight 70according to the intensity of the external light Le, so that a powerconsumption of the backlight 70 decreases in a place where the intensityof the external light Le is high.

A test circuit 110 is arranged in a peripheral area PA of the displaypanel 50. The test circuit 110 is used to test the built-in light sensor51 during a test procedure of the display panel 50.

The test circuit 110 is electrically connected to the built-in lightsensor 51 and a test pixel part 120 in response to an enable signal Venduring the test procedure. However, when the driving chip 55 is mountedon the display panel 50 and a gate low voltage is applied to a lowvoltage bump B-vgl, the test circuit 110 is electrically separated fromthe built-in light sensor 51 and the test pixel part 120. Thus, the testcircuit 110 does not affect any influence to the built-in light sensor51 and the test pixel part 120 during an active period of the displaypanel 50.

According to the above, the test circuit 110 connected to the built-inlight sensor 51 is arranged on the display panel 50 to test the built-inlight sensor 51 that senses the intensity of the external light. Thebrightness of the pixels operated by the test circuit 110 is measured bythe brightness measurer 130. Thus, the light sensor test unit 100 maytest whether the built-in light sensor 51 is normally operated.

While the present invention has been shown and described with referenceto some exemplary embodiments thereof, it should be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope of thepresent invention as defined by the appended claims.

1. A method of testing a light sensor built in a display panel, to sensean external light, comprising: providing a predetermined external lightto the light sensor: outputting a sensing signal corresponding to theexternal light through an output node of the light sensor: outputting adriving signal to pixels selected from a plurality of pixels arranged inthe display panel in response to the sensing signal by using a testcircuit arranged in a peripheral area of the display panel: displaying agray-scale corresponding to the driving signal through the selectedpixels on a screen of the display panel: measuring a brightnesscorresponding to the gray-scale in a region where the selected pixelsare arranged by using a brightness measurer positioned above the screenof the display panel; and comparing the measured brightness with apredetermined reference brightness to test whether the light sensor isnormally operated.
 2. The method of claim 1, wherein the outputting ofthe driving signal in response to the sensing signal comprises:switching the sensing signal in response to an enable signal; outputtingeither a first voltage or a second voltage as the driving voltage inresponse to the sensing signal; and switching the driving signal inresponse to the enable signal.
 3. The method of claim 2, wherein thefirst voltage is a driving voltage of the display panel, and the secondvoltage is a ground voltage.
 4. The method of claim 3, wherein the firstvoltage is output as the driving signal when the sensing signal is atlow level, and the second voltage is output as the driving signal whenthe sensing signal is at high level.
 5. The method of claim 2, prior toproviding the predetermined external light to the light sensor, furthercomprising: applying a sensing gate signal in a high state to the lightsensor and outputting the sensing signal in a high state through theoutput node; changing the sensing signal in the high state to the secondvoltage in response to the enable signal; and initializing the drivingsignal applied to the selected pixels to the second voltage in responseto the enable signal.
 6. The method of claim 1, prior to outputting thedriving signal to the selected pixels, further comprising: applying agate signal to the pixels arranged in the display panel.
 7. A displayapparatus comprising: a backlight unit which generates an internallight; a display panel including a plurality of pixels which is arrangedin a display area and receives the internal light to display an image,and a light sensor which is arranged in a black matrix area adjacent tothe display area and outputs a sensing signal corresponding to anintensity of an external light; a backlight driver which receives thesensing signal to control an intensity of the internal light generatedfrom the backlight unit; and a display panel driver driving the pixelsarranged in the display panel, and wherein the display panel furthercomprises: a test circuit connected to an output node of the lightsensor, which outputs a driving signal in response to the sensing signaloutput from the output node of the light sensor when the external lighthaving a predetermined intensity is provided to the light sensor inorder to test the light sensor, and pixels selected from the pixelswhich receive the driving signal from the test circuit to display agray-scale corresponding to the driving signal on a screen of thedisplay panel during the test process of the light sensor, wherein thetest circuit is arranged in a peripheral area of the display panel, anda brightness measure is positioned above the screen of the display panelto measure the brightness of the selected pixels.
 8. The displayapparatus of claim 7, wherein the display panel driver is formed in achip and mounted in a chip mounting area arranged outside the blackmatrix area of the display panel, and the test circuit is arrangedadjacent to the chip mounting area.
 9. The display apparatus of claim 8,wherein the test circuit comprises: a first switching device connectedto the output node which outputs the sensing signal from the output nodein response to an enable signal; an inverter which outputs either afirst voltage or a second voltage as the driving signal in response tothe sensing signal output from the first switching device; and a secondswitching device which switches the driving signal output from theinverter in response to the enable signal.
 10. The display apparatus ofclaim 9, wherein the test circuit further comprises an enable terminalconnected to the first and second switching devices which applies theenable signal.
 11. The display apparatus of claim 10, wherein the pixelsare driven in response to a gate signal, and the enable terminal isconnected to a low voltage bump which receives a gate low voltage whichdetermines a low level of the gate signal from a driving chip amongbumps arranged on the display panel in order to be electricallyconnected to the driving chip mounted on the display panel.